[ir.rupt] vi [L irruptus, pp. of irrumpere, fr. in- + rumpere to break--more at reave] (1886) 1: to rush in forcibly or violently
2. of a natural population: to undergo a sudden upsurge in numbers esp. when natural ecological balances and checks are disturbed
3: erupt 1c "the crowd ~ed in a fervor of patriotism --Time" -- ir.rup.tion n